I think I figured it out - it's the v70.00.335 update.up file. Duh on my part.I have read the EXTRA INSTRUCTIONS FOR FW v70.00.335 multiple times, including the top-line:
You will need: the “update.up” file, ID7_Recovery_XX, Computer connected via serial connection, Putty or SecureCRT.
Nowhere can I find the "update.up" file mentioned. Can anyone paste it in a reply or point me to where it is please?